@6Dasher
Clearly it can't be quantified to everyone's or anyone's satisfaction as this question has been asked since day one. This site has the optics reputation it does because we have explored it, not just me but others. No two people see things the same, exactly like no two barrels are the same... it's identical.
This test and thread clearly demonstrates that.
A scope is a telescopic SIGHT, emphasis on SIGHT. It is not a camera lens, (And recently it has been done on camera sites to show the average user cannot tell the difference between a $300 Nikon lens and $2000 one) where great quality optics for cameras comes into play is when you "Blow up" the image. The higher degree of sharpness becomes apparent, however for everyday use, and viewing on a computer, unless you make a living taking pictures, you will never know or see the difference.
Also we are not trying to type and color code birds. CA is meaningless to the average shooter. (Again look at TEAM GAP) Guys are cleaning up in tactical competitions right now using the Bushnell XRS which has quite a bit of CA. As well I can show you tons of it with my Zeiss / Hensoldt. It's generally considered the top brand optically but still they have much more CA than any other brand. I can demonstrate this with no less than 4 Hensoldts have in my possession including the new 3-26x. CA is meaningless to a shooter.
What you are debating has no bearing on the shooter. The only valid argument is for low light and difficult light situations when you are trying to resolve a camouflaged animal out of the shadows. (See my 8X56mm comment)
if quantifying it was easy, it would have been done years ago, yet here we are. Prime example, the results NF put on the table with this test, and people's reaction including the testers.
It's subjective, and exactly like comparing different ammo to any rifle out there. These tests require people who every bit the variations barrels do. The human mind can be tricked and we trick ourselves all the time into believing we are seeing something we are not or that what we are seeing has repercussions when they don't.
Nobody has hit on the magic formula to quantify a scope, nobody.